1. Field of the Invention
The present invention relates to a powder filling apparatus capable of filling a container with powder, such as toner used for an image forming apparatus, with high density and at high speed, and a method for filling a container with powder. The present invention also relates to a cleaner used for removing powder attached to a nozzle of the powder filling apparatus through which the powder drops.
2. Description of the Related Art:
Toner used for an image forming apparatus such as an electrophotographic copying machine is normally contained in a bottle or other containers having a cylindrical or rectangular parallelepiped shape for transportation and storage. Conventionally, such a container is filled with toner by placing it under a toner feed device to receive toner dropping by free-fall.
However, because air is present in the container, the drop speed of toner is reduced, and the toner accumulated in the container is mixed with the air. As a result, the bulk density of the toner in the container is reduced, and thus it is not possible to feed a required amount of toner to the container at one time by free-fall. Instead, in practice, about half the amount of toner required for filling the container is first fed by gravity, for example. Then, after an elapse of a predetermined time period during which the toner in the container has set%led, the remaining amount of the toner is fed. However, this is not an effective method for feeding toner to the container. The operational efficiency thereof is very low.
Japanese Laid-Open Patent Publication No. 1-124503 discloses an apparatus in which a container is first evacuated and powder is fed into the evacuated container from a powder feed device at high speed at one time by using the difference between the pressure in the container and that in the powder feed device, thus filling the container with powder with high density.
In the above-described apparatus, the container is placed in an evacuation case, and both the inside and the outside of the container is evacuated. A nozzle is disposed at the bottom end of a hopper storing toner. A bottom opening of the nozzle is opened and closed by the vertical movement of a conical valve element tapered upward. The end portion of the nozzle is located inside the evacuation case in which the container is placed. When toner is fed into the container, the inside and the outside of the container are first evacuated in the evacuation case, and a toner inlet of the container is fitted to the end portion of the nozzle. Then, the valve element is moved downward to release the bottom opening of the nozzle. This allows the toner stored in the hopper to drop into the container at high speed through the nozzle to fill the container with the toner. Simultaneously with the drop of the toner, air is introduced to the evacuation case so that the atmospheric pressure is resumed, thus preventing the container from being broken by the high-speed toner drop.
The above-described apparatus solves the problem of reducing the bulk density of powder accumulated in the container because the container has been evacuated before the powder is fed thereinto and thus does not contain air.
However, the above-described method requires complicated steps which include placing the container in the evacuation case under the condition of the nozzle being opened with the valve element, evacuating the evacuation case to evacuate the inside of the container, and then feeding the powder into the container by opening the nozzle with the valve element. Thus, a longer time is required for filling a single container, which reduces the operational efficiency.
Further, because the toner drops into the container at high speed and the container is evacuated, the toner accumulated in the container may be excessively compressed. Especially, at the time immediately after the start of the toner feeding, when the pressure in the container is greatly different from that in the hopper, the toner dropping inside the container violently collides against the bottom of the container, thereby producing a great force exerted on the toner. As a result, the toner may be lumped at the bottom of the container depending on the size of the toner particles. When a container having such a lump of toner is mounted on an image forming apparatus to be used for image formation, the toner will not be smoothly supplied from the container to the apparatus.
Moreover, when the toner dropping from the hopper at high speed passes through the lower narrowed portion of the hopper, a great force is exerted on the dropping toner. At this time, air contained in the toner is greatly compressed as it comes closer to the lower portion of the hopper. This may cause the air to be blown upward before flowing down from the hopper, and thus the powder remaining in the hopper may be blown upward, partly scattered out of the hopper. When some of the toner is scattered outside, the predetermined amount of toner can not be fed to the container.
Furthermore, in case where the bottom opening of the nozzle and the toner inlet of the container are not completely sealed with each other, the toner may be scattered through the gap therebetween. The toner attached to the outer circumference of the nozzle may be swept off therefrom when a new container is fitted to the nozzle. This results in contaminating the container and the neighboring area. The toner scattered from the container also contaminates the container and the neighboring area. To remove such toner attaching to the container and scattered to the neighboring area, it is necessary to temporarily stop the filling operation, which greatly lowers the operational efficiency.